1. Field of the Invention
The present invention relates to a rewritable recording medium (including write-once type) where a digital signal such as PCM audio data to be recorded is inserted in a video format signal (a signal having the same format as a television signal including horizontal and vertical sync signals), a rewritable (also including write-once type) recording medium with pregrooves, and a recording/reproducing apparatus therefor.
2. Description of Background Information
There is a known multiplex recording method, wherein a digital signal such as a PCM audio data is inserted into the vertical blanking period of a video format signal, to be recorded on a rewritable recording disk. This method is suitable for a so-called "postrecording" by which audio data matched with image information carried by a video format signal is recorded after the recording of the image information.
The vertical blanking period of a video format signal however includes an identification (ID) signal having at least time axis information such as a so-called Philips code, so that inserting a digital signal into the vertical blanking period therefore may erase the ID signal.
There is known a rewritable recording medium which has wavy pregrooves to carry track ID information including track numbers.
In order to record information on a target track on such a rewritable recording medium or read out recorded information therefrom, it is necessary to identify its track number. In the conventional rewritable recording mediums, the same track number is recorded in the same pregroove, and information to be rewritten is recorded in the pregrooves.
Because the flatness at the bottom of the pregrooves is not enough, however, information, when recorded in the pregrooves, would have noise thereon, resulting in low C/N of the reproduced information signal.
As a solution to this shortcoming, information to be recorded may be recorded not on the pregrooves, but on lands having better flatness, each located between two adjacent pregrooves, to improve C/N.
In recording information on a land, however, the track numbers are identified from pregrooves on both sides of the land, so that two different track numbers may be read out at a time, raising a new problem.